In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a circumferential surface of a photosensitive drum as the photosensitive drum is rotated, and then toner is supplied from a development roller to the circumferential surface of the photosensitive drum. Accordingly, the electrostatic latent image is developed into a toner image, and the toner image is coated on the circumferential surface of the photosensitive drum. On the downstream side in a rotating direction of the photosensitive drum against the development roller, a transfer roller is oppositely arranged on the photosensitive drum. At the time the toner image coated on the circumferential surface of the photosensitive drum comes to be opposite to the circumferential surface of the transfer roller as the photosensitive drum is rotated, a paper is supplied between the photosensitive drum and the transfer roller. Also, by the action of a bias applied to the transfer roller, the toner image is transferred from the circumferential surface of the photosensitive drum onto the paper to form an image (toner image) on the paper.
In the image forming apparatus as described above, a so-called double-sided mode is provided, in which an image is formed on one surface of a paper, the paper is transported with its sides reversed, and then an image is formed on the other side that is the reverse of the one surface of the paper.
In the image forming apparatus having the double-sided mode, for example, there are installed a main transport path for transporting a paper up to a paper discharge port via an image forming portion having a photosensitive drum provided therein, and a sub-transport path for sending the paper, on one surface of which an image is formed by the image forming portion, to the image forming portion with the sides of the paper reversed.
Rollers, which are provided in the photosensitive drum, the main transport path, and the sub-transport path, are rotated, for example, by an output of a single reversible motor. That is, by the output of forward rotation of the reversible motor, the photosensitive drum is rotated, and the respective rollers in the main transport path are rotated. Accordingly, the paper is transported to the main transport path, and a toner image is transferred from the photosensitive drum to the paper. On the other hand, by the output of reverse rotation of the reversible motor, the respective rollers in the sub-transport path are rotated, and the paper is transported to the sub-transport path. From the viewpoint of suppressing deterioration of the photosensitive drum, for example, a clutch is installed between the reversible motor and the photosensitive drum, and during the reverse rotation of the reversible motor, the connection between the reversible motor and the photosensitive drum is released by the clutch.